Method and system for control of a patient's body temperature by way of a transluminally insertable heat exchange catheter

Abstract

Methods and apparatuses for temperature modification of a patient, or selected regions thereof, including an induced state of hypothermia. The temperature modification is accomplished using an in-dwelling heat exchange catheter within which a fluid heat exchange medium circulates. A heat exchange cassette of any one of several disclosed variations is attached to the circulatory conduits of the catheter, the heat exchange cassette being sized to engage a cavity within one of various described re-usable control units. The control units include a heater/cooler device, a user input device, and a processor connected to receive input from various sensors around the body and the system. The heater/cooler device may be thermoelectric to enable both heating and cooling based on polarity. A temperature control scheme for ramping the body temperature up or down without overshoot is provided. The disposable heat exchange cassettes may include an integral pump head that engages with a pump drive mechanism within the re-usable control unit. More than one control unit may be provided to receive the same heat exchange cassette so that, for example, a large capacity control unit can be used initially, and a smaller, battery-powered unit can be substituted once the patient reaches the desired target temperature.

What is claimed is:  
     
       1. A controller for controlling the temperature and flow of a heat exchange fluid within a circuit, comprising: 
       a heat exchange catheter insertable within a patient, the catheter configured to heat or cool blood flowing past the catheter within the patient;  
       an external heat exchanger;  
       a pump for flowing heat exchange fluid through the circuit;  
       a thermoelectric heating and/or cooling element, the thermoelectric heating and/or cooling element being in non-fluid thermal contact with the external heat exchanger containing the heat exchange fluid;  
       a patient sensor positioned and configured to generate a signal representing a biophysical condition of a patient;  
       a microprocessor connected to receive the signal from the patient sensor and being responsive to the signal to control the thermoelectric heating and/or cooling element;  
       a mechanical drive unit for activating the pump contained in the circuit; and  
       a safety sensor for detecting a fluid parameter representing the presence of air in the circuit and generating a safety signal representative of the presence or absence of the fluid parameter, the safety signal being transmitted to the microprocessor that responds by controlling the flow of heat exchange fluid within the circuit.  
     
     
       2. The controller of  claim 1 , wherein the safety sensor further comprises an optical fluid level detector positioned to optically sense the fluid level within the circuit. 
     
     
       3. The controller of  claim 2  wherein the optical fluid level detector includes an optical beam source and an optical sensor, wherein the optical beam source and optical sensor are positioned adjacent the circuit to sense the level of fluid therein. 
     
     
       4. The controller of  claim 1  further comprising a plurality of the patient sensors for sensing biophysical conditions of a patient, the microprocessor being responsive to each of the sensors to control the generating element. 
     
     
       5. The controller of  claim 4 , wherein the microprocessor is configured to compare the signals from at least two of the plurality of patient sensors and produce an alarm condition when the signals do not agree. 
     
     
       6. The controller of  claim 1  wherein the microprocessor further receives a target temperature input, and the signal represents a sensed patient temperature, the microprocessor is configured to add heat to the fluid if the target temperature is above the patient temperature and remove heat from the fluid if the target temperature is below the patient temperature, and wherein the microprocessor responds to the signal from the patient sensor with a proportional integrated differential (PID) response such that the rate at which patient temperature approaches the target temperature is controlled. 
     
     
       7. A controller for controlling the temperature and flow of a heat exchange fluid within a circuit, comprising: 
       a heat exchange catheter insertable within a patient, the catheter configured to heat or cool blood flowing past the catheter within the patient;  
       an external heat exchanger;  
       a pump for flowing heat exchange fluid through the circuit;  
       a thermoelectric heating and/or cooling element, the thermoelectric heating and/or cooling element being in non-fluid thermal contact with the external heat exchanger containing the heat exchange fluid;  
       a patient sensor positioned and configured to generate a signal representing a biophysical condition of a patient;  
       a microprocessor connected to receive the signal from the patient sensor and being responsive to the signal to control the thermoelectric heating and/or cooling element;  
       a mechanical drive unit for activating the pump contained in the circuit; and  
       a bubble detector for detecting gas entrained in the heat exchange fluid, and for generating a safety signal representing the presence of bubbles within the circuit, the safety signal being transmitted to the microprocessor that responds by controlling the flow of heat exchange fluid within the circuit.  
     
     
       8. A controller for controlling the temperature and flow of a heat exchange fluid within a circuit, comprising: 
       a heat exchange catheter insertable within a patient, the catheter configured to heat or cool blood flowing past the catheter within the patient;  
       an external heat exchanger;  
       a pump for flowing heat exchange fluid through the circuit;  
       a thermoelectric heating and/or cooling element, the thermoelectric heating and/or cooling element being in non-fluid thermal contact with the external heat exchanger containing the heat exchange fluid;  
       a mechanical drive unit for activating the pump contained in the circuit for pumping the heat exchange fluid;  
       a microprocessor connected to control both the thermoelectric heating and/or cooling element and the mechanical drive unit; and  
       a safety system for detecting problems in the circuit, the safety system including a plurality of sensors that generate signals indicative of respective parameters of the system and/or patient, at least one of the sensors for detecting the presence of air in the heat exchange fluid, the signals being transmitted to the microprocessor that responds by controlling the flow of the heat exchange fluid within the circuit.  
     
     
       9. The controller of  claim 8 , wherein the safety system includes a sensor for detecting the fluid level within the circuit. 
     
     
       10. The controller of  claim 8 , wherein the safety system includes a sensor for detecting the temperature of a location within the patient. 
     
     
       11. The controller of  claim 10 , further including a redundant sensor for detecting the temperature of a location within the patient, the microprocessor being responsive to a difference in the temperatures sensed by the sensor and the redundant sensor. 
     
     
       12. A controller for controlling the temperature and flow of a heat exchange fluid within a circuit, comprising: 
       a heat exchange catheter insertable within a patient, the catheter configured to heat or cool blood flowing past the catheter within the patient;  
       an external heat exchanger;  
       a pump for flowing heat exchange fluid through the circuit;  
       a thermoelectric heating and/or cooling element, the thermoelectric heating and/or cooling element being in non-fluid thermal contact with the external heat exchanger containing the heat exchange fluid;  
       a mechanical drive unit for activating the pump contained in the circuit for pumping the heat exchange fluid;  
       a microprocessor connected to control both the thermoelectric heating and/or cooling element and the mechanical drive unit; and  
       a safety system for detecting problems in the circuit, the safety system including a plurality of sensors that generate signals indicative of respective parameters of the system and/or patient, at least one of the sensors for detecting bubbles within the circuit, the signals being transmitted to the microprocessor that responds by controlling the flow of the heat exchange fluid within the circuit.  
     
     
       13. A controller for controlling the temperature and flow of a heat exchange fluid within a circuit, the circuit comprising a heat exchange catheter insertable within a patient, an external heat exchanger, and a pump for flowing heat exchange fluid through the circuit, the controller comprising: 
       a heat and/or cold generating element, the generating element being in thermal contact with the external heat exchanger containing the heat exchange fluid;  
       a mechanical drive unit for activating the pump contained in the circuit for pumping the heat exchange fluid;  
       a microprocessor connected to control both the generating element and the mechanical drive unit; and  
       a safety system for detecting problems in the circuit, the safety system including a plurality of sensors that generate signals indicative of respective parameters of the system and/or patient, the signals being transmitted to the microprocessor that responds by  
       controlling the operation of the generating element and the mechanical drive unit, wherein the safety system includes a sensor for detecting the operating status of the generating element.  
     
     
       14. A controller for controlling the temperature and flow of a heat exchange fluid within a circuit, the circuit comprising a heat exchange catheter insertable within a patient, an external heat exchanger, and a pump for flowing heat exchange fluid through the circuit, the controller comprising: 
       a heat and/or cold generating element, the generating element being in thermal contact with the external heat exchanger containing the heat exchange fluid;  
       a mechanical drive unit for activating the pump contained in the circuit for pumping the heat exchange fluid;  
       a microprocessor connected to control both the generating element and the mechanical drive unit; and  
       a safety system for detecting problems in the circuit, the safety system including a plurality of sensors that generate signals indicative of respective parameters of the system and/or patient, the signals being transmitted to the microprocessor that responds by  
       controlling the operation of the generating element and the mechanical drive unit, wherein the safety system includes a sensor for detecting the operating status of the mechanical drive unit.